The truck came with a white plastic card in the owner's manual that had the code. If you don't have that then you need to get a dealership to plug the computer in and pull the code.
If you know which dealership sold the truck, and you go to the dealership, then they may have the code on file.
We have all the codes on file for any vehicle we have sold in the last 6 years. However, I want to see your registration and driver's license to ensure you are the owner of the vehicle. There are way too many scams out there to give it out with out those two pieces of ID.
PM me your vin number and I will tell you who the original dealership was.